Multi-tube reactor systems and processes for no-oxidative conversion of methane

ABSTRACT

The present disclosure refers to systems and methods for efficiently converting a C 1 -C 3  alkane such as natural gas to a liquid C 2 -C 10  product and hydrogen. Generally, the process comprises flowing the C 1 -C 3  alkane through a plurality of tubes within a vessel wherein the tubes house a catalyst for converting the C 1 -C 3  alkane to the liquid C 2 -C 10  product and hydrogen. The C 1 -C 3  alkane is heated under suitable conditions to produce the liquid C 2 -C 10  product and hydrogen. Advantageously, the C 1 -C 3  alkane is heated by burning a fuel outside the tubes in fuel burning nozzles configured to transfer heat from the burning through the tubes.

FIELD OF THE DISCLOSURE

The present disclosure relates to systems and methods for converting aC₁-C₃ alkane to a liquid C₂-C₁₀ product and hydrogen.

BACKGROUND AND SUMMARY

Hydrogen is one of the more important options for future clean energy.In addition, higher molecular weight hydrocarbons such as olefins andaromatics are often desirable as value added chemicals. While methanehas been used to make such value added chemicals in the past the processare usually not cost-effective. What is needed is a solution thatproduces hydrogen and value added chemicals in a cost-effective manner.It would further be advantageous if such a solution was not energyintensive.

Advantageously, the instant application pertains to new systems andmethods that advantageously produce hydrogen and value added chemicalsin a cost-effective manner and are not energy intensive.

In one embodiment the application pertains to a process for converting aC₁-C₃ alkane to a liquid C₂-C₁₀ product and hydrogen. The processcomprises flowing the C₁-C₃ alkane through a plurality of tubes within avessel wherein the tubes house a catalyst for converting the C₁-C₃alkane to the liquid C₂-C₁₀ product and hydrogen. The C₁-C₃ alkane isheated under suitable conditions to produce the liquid C₂-C₁₀ productand hydrogen. The C₁-C₃ alkane is heated by burning a fuel outside thetubes in fuel burning nozzles configured to transfer heat from theburning through the tubes.

In another embodiment the application pertains to a process forconverting natural gas to a liquid C₂-C₁₀ product comprising ethylene,benzene, naphthalene, or a mixture thereof and hydrogen. The processcomprises flowing the natural gas through a plurality of tubes within avessel wherein the tubes house a catalyst for converting the natural gasto the liquid C₂-C₁₀ product comprising ethylene, benzene, naphthalene,or a mixture thereof and hydrogen. The natural gas is heated at atemperature of from about 500, or from about 700, up to about 1000 or upto about 1200° C., and a pressure of from about 1 atmosphere up to about3, or up to about 5, or up to about 10, or up to about 20 atmospheres toproduce the liquid C₂-C₁₀ product comprising ethylene, benzene,naphthalene, or a mixture thereof and hydrogen. The natural gas isheated by burning a fuel outside the tubes in fuel burning nozzlesconfigured to transfer heat from the burning through the tubes.Additionally or alternatively, electric or other heating may be employedwith the burning fuel or in place of it.

In another embodiment the application pertains to a reactor forconversion of alkanes to liquid hydrocarbons and hydrogen. The reactorcomprises a vessel and a plurality of tubes within the vessel whereinthe tubes are configured to house a catalyst. The vessel is configuredto burn a fuel outside the plurality of tubes. The vessel is furtherconfigured to transfer heat from the burning fuel to the catalyst housedwithin the plurality of tubes.

These and other objects, features and advantages of the exemplaryembodiments of the present disclosure will become apparent upon readingthe following detailed description of the exemplary embodiments of thepresent disclosure, when taken in conjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure, together with furtherobjects and advantages, may best be understood by reference to thefollowing description taken in conjunction with the accompanyingdrawings.

FIG. 1 shows reaction temperature, pressure, and equilibrium conversionfor a methane to benzene reaction.

FIG. 2 shows a representative multi-tube reactor with top fired heater.

DETAILED DESCRIPTION

The following description of embodiments provides a non-limitingrepresentative examples referencing numerals to particularly describefeatures and teachings of different aspects of the invention. Theembodiments described should be recognized as capable of implementationseparately, or in combination, with other embodiments from thedescription of the embodiments. A person of ordinary skill in the artreviewing the description of embodiments should be able to learn andunderstand the different described aspects of the invention. Thedescription of embodiments should facilitate understanding of theinvention to such an extent that other implementations, not specificallycovered but within the knowledge of a person of skill in the art havingread the description of embodiments, would be understood to beconsistent with an application of the invention.

General Process

The instant application pertains to a process for converting a C₁-C₃alkane to a liquid C₂-C₁₀ product and hydrogen. The process generallycomprises first flowing the C₁-C₃ alkane through a plurality of tubeswithin a vessel. The tubes typically house a catalyst for converting theC₁-C₃ alkane to the liquid C₂-C₁₀ product and hydrogen. The C₁-C₃ alkaneis not particularly limited and may include, for example, natural gas,methane, ethane, propane, or mixtures thereof. As used herein naturalgas comprises methane and potentially higher alkanes, carbon dioxide,nitrogen or other gases, and/or sulfide compounds such as hydrogensulfide, and mixtures thereof. The produced product typically comprisesliquid C₂-C₁₀ product and hydrogen. The liquid C₂-C₁₀ product is notparticularly limited and could be saturated, unsaturated, aromatic, or amixture of such compounds. In some embodiments the liquid C₂-C₁₀ productmay comprise ethylene, benzene, naphthalene, and various mixturesthereof depending upon the desired products and reactions used.

The C₁-C₃ alkane is usually heated under suitable conditions in thepresence of the catalyst to produce the liquid C₂-C₁₀ product andhydrogen. Suitable conditions may vary depending upon the reactants,desired products, catalysts, and equipment employed. Typically, atemperature of from about 500, or from about 700, up to about 1000 or upto about 1200° C., and a pressure of from about 1 atmosphere up to about3, or up to about 5, or up to about 10, or up to about 20 atmospheresmay be employed to produce the liquid C₂-C₁₀ product that may compriseethylene, benzene, naphthalene, or a mixture thereof and hydrogen. Insome embodiments the C₁-C₃ alkane is heated by burning a fuel outsidethe tubes in fuel burning nozzles configured to transfer heat from theburning through the tubes. As described below, the hydrogen produced maybe used as the fuel in the fuel burning nozzles outside the tubes.

Catalyst

The catalyst composition, form, size, shape, and properties may varydepending upon such parameters as the reactants, reactor type, tube sizeand shape, reaction conditions, and/or desired products. In someembodiments the catalyst comprises substantially cylindrical pellets.The catalyst pellets may comprise one or more holes passing through thelength of the pellet, may be domed shaped on the ends, and/or maycomprise a plurality of grooves on the pellet surface. Suitable catalystpellets are described in, for example, U.S. publication US2021/0115341to Sampath which published on Apr. 22, 2021 and is incorporated byreference herein.

In some embodiments the aspect ratio (ratio of height to diameter orcross-section length) of catalyst pellets may be at least 0.3, or atleast 0.5 up to about 3, or up to about 2. In some embodiments thecatalyst may comprise catalyst pellets of from about 0.5 to about 1.0,or to about 2.0 inches in diameter. In some embodiments the catalystpellets are substantially cylindrical and wherein at least a portion ofthe pellets comprise one or more holes passing through the length of thepellet. The holes passing through the catalyst pellets assist inincreasing the external surface area and hence generally decrease thecharacteristic length of the catalyst pellets to ensure adequate masstransfer rate. It may be desirable to have a characteristic length,defined as the pellet volume divided by the external surface area, to besmaller than 0.3, or smaller than 0.2, or smaller than 0.15 cm. Withadequate porosity and pore structure the effective diffusivity for lighthydrocarbons may be in the range of 5×10{circumflex over ( )}-3 to2×10{circumflex over ( )}-2 cm²/s, and the catalyst effectiveness factormay be in the range of from 0.05, or from 0.1 up to 0.5, or up to 0.4.

The catalyst may comprise washcoated honeycomb monolith catalyst ormetal monolith in some embodiments. The monolith may comprise ceramic,silica, quartz, glass, metal, silicon carbide, silicon nitride, boronnitride, a metal oxide or any combination thereof. Suitable metal oxidesmay comprise titania, iron oxide, zirconia, a mixed metal oxide, or anycombination thereof.

Reactor Tubes

Like the catalyst, the tubes in the reactor may vary in shape, size,material, and/or properties depending upon such parameters as thereactants, reactor type, reaction conditions, and/or desired products.The plurality of tubes may comprise a ceramic, a metal, or a mixturethereof. Suitable metals may include, for example, alloy 800, alloy800/HT, alloy 309, any other metallurgy suitable for high temperatureservices, or a mixture thereof.

In some embodiments the tubes are configured to minimize or lessenpressure drop. For example, the tubes may be configured such that apressure drop within the plurality of tubes comprises less than about 45psig.

If desired the plurality of tubes may comprise one or metal insertswithin the plurality of tubes to facilitate the transfer of heat in aradial direction within the plurality of tubes. The metal insert maycomprise a screen, a plate, or a combination thereof.

In this manner the effective thermal conductivity in a radial directionmay be from about 5 to about 200 W/mK while the temperature drop may beless than 50 to 200° C. The plurality of tubes may also be configuredsuch that the heating duty per tube is from about 2 kW/m² tube to about70 kW/m²-tube. The size of the tubes may vary depending upon the desiredheat transfer and other properties of the system. In some embodiments, amajority of the plurality of tubes within the vessel have a diameter offrom about 1, or from about 2 up to about 6, or up to about 7 inches. Insome embodiments, one or more of the plurality of tubes within thevessel may have a diameter of from about 1, or from about 2 up to about6, or up to about 7 inches.

Generally, the reactor comprises fuel burning nozzles outside and alongthe length of the plurality of tubes in order to burn fuel outside theplurality of tubes. The fuel is not particularly critical so long as itis capable of heating the tubes adequately. In some embodiments the fuelcomprises a hydrocarbon, hydrogen, or a mixture thereof. In someembodiments the fuel may comprise hydrogen formed in the process. Insome embodiments at least a portion of the heat used in heating theC₁-C₃ alkane in the tubes comprises heat from a flue gas generatedduring a catalyst regeneration.

FIG. 1 shows reaction temperature, pressure, and equilibrium conversionfor a methane to benzene reaction according to the above embodiments.

FIG. 2 shows a representative multi-tube reactor with top fired heater.In this embodiment feed enters the tube from the top and passes over thecatalyst in the tubes. The tubes comprising catalyst and feed are heatedusing fuel burning adjacent or near the tubes. The product of thecatalytic reaction exits at the bottom of the reactor.

In the preceding specification, various embodiments have been describedwith references to the accompanying drawings. It will, however, beevident that various modifications and changes may be made thereto, andadditional embodiments may be implemented, without departing from thebroader scope of the invention as set forth in the claims that follow.The specification and drawings are accordingly to be regarded as anillustrative rather than restrictive sense.

1. (canceled)
 2. The process of claim 11 wherein the C₁-C₃ alkanecomprises natural gas.
 3. The process of claim 11 wherein the liquidC₂-C₁₀ product comprises ethylene, benzene, naphthalene, or a mixturethereof.
 4. The process of claim 11 further comprising employing one ormore metal inserts within the plurality of tubes to facilitate thetransfer of heat in a radial direction within the plurality of tubes. 5.The process of claim 11 wherein the fuel comprises a hydrocarbon,hydrogen, or a mixture thereof.
 6. The process of claim 5 wherein atleast a portion of the fuel comprises hydrogen formed in the process. 7.The process of claim 11 wherein at least a portion of the heat used inheating the C₁-C₃ alkane comprises heat from a flue gas generated duringa catalyst regeneration.
 8. The process of claim 11 wherein a pressuredrop within the plurality of tubes comprises less than about 45 psig. 9.The process of claim 11 wherein a majority of the plurality of tubeswithin the vessel have a diameter of from about 2 to about 6 inches. 10.The process of claim 11 wherein the catalyst comprises catalyst pelletsof from about 0.5 to about 1.0 inches in diameter.
 11. A process forconverting a C₁-C₃ alkane to a liquid C₂-C₁₀ product and hydrogenwherein the process comprises: flowing the C₁-C₃ alkane through aplurality of tubes within a vessel wherein the tubes house a catalystfor converting the C₁-C₃ alkane to the liquid C₂-C₁₀ product andhydrogen; and heating the C₁-C₃ alkane under suitable conditions toproduce the liquid C₂-C₁₀ product and hydrogen; wherein the C₁-C₃ alkaneis heated by burning a fuel outside the tubes in fuel burning nozzlesconfigured to transfer heat from the burning through the tubes; whereinthe catalyst comprises substantially cylindrical pellets and wherein atleast a portion of the pellets comprise one or more holes passingthrough the length of the pellet, are domed shaped on the ends, comprisea plurality of grooves on the pellet surface, and have an aspect ratioof at least 0.5 up to about
 2. 12. The process of claim 11 wherein thecatalyst comprises a washcoated honeycomb monolith catalyst wherein thewashcoated monolith catalyst comprises ceramic, silica, quartz, glass,metal, silicon carbide, silicon nitride, boron nitride, a metal oxide orany combination thereof.
 13. The process of claim 12 wherein the metaloxide comprises titania, iron oxide, zirconia, a mixed metal oxide, orany combination thereof.
 14. The process of claim 11 wherein thecatalyst comprises metal monolith.
 15. The process of claim 11 whereinthe catalyst effectiveness factor is from about 0.05 to about 0.5.
 16. Aprocess for converting natural gas to a liquid C₂-C₁₀ product comprisingethylene, benzene, naphthalene, or a mixture thereof and hydrogenwherein the process comprises: flowing the natural gas through aplurality of tubes within a vessel wherein the tubes house a catalystfor converting the natural gas to the liquid C₂-C₁₀ product comprisingethylene, benzene, naphthalene, or a mixture thereof and hydrogen; andheating the natural gas at a temperature of from about 700 to about1000° C. and a pressure of from about 1 to about 3 atmospheres toproduce the liquid C₂-C₁₀ product comprising ethylene, benzene,naphthalene, or a mixture thereof and hydrogen; wherein the natural gasis heated by burning a fuel outside the tubes in fuel burning nozzlesconfigured to transfer heat from the burning through the tubes; whereinthe catalyst comprises substantially cylindrical pellets and wherein atleast a portion of the pellets comprise one or more holes passingthrough the length of the pellet, are domed shaped on the ends, comprisea plurality of grooves on the pellet surface, and have an aspect ratioof at least 0.5 up to about
 2. 17-27. (canceled)